Security documents that must be verifiable on their authenticity are e.g. all kinds of identification documents such as passports, visas, identity cards, driver licenses, bank cards, credit cards, security entrance cards, and further value-documents such as banknotes, shares, bonds, certificates, cheques, lottery tickets and all kinds of entrance tickets such as airplane tickets and railroad season-tickets.
Said security documents are in many cases made by the lamination of a data containing card. Said laminate can be single-sided when f.i. a card is laminated on a paper support as in a passport. It is required that said laminates are foolproof. However most laminates delaminate when heated at about 100.degree. C. This poses a serious problem.